Endodontic treatment of permanent teeth with open apexes using calcium hydroxide and mineral trioxide aggregate should be compared. Medical histories of all patients were noncontributory. After clinical and radiographic investigation the pulp chamber was exposed after rubber dam placement. The working length of the canal was determined with a conventional or digital radiograph. The canal was instrumented with hand files. Sodium hypochlorite (2 per cent) was used as an irrigant. Method 1: the root canals were carefully dried and filled with a calcium hydroxide paste (Calcicur, Voco, Cuxhaven, Germany). The calcium hydroxide dressings were changed every two months until a calcific barrier formed at the apex after an average period of 16 months. Method 2: the calcium hydroxide dressing was changed twice in intervals of 15 days. Then mineral trioxide aggregate was placed for apical barrier formation. Six hours later, the canal was obturated. All canals were obturated by using a warm gutta-percha technique (ObturaTM, Obtura Corporation, Texceed, USA) and a sealer (SealapexTM, Kerr, Karlsruhe, Germany). Using a calcium hydroxide paste in combination with mineral trioxide aggregate for apical barrier formation it is possible to reduce the treatment time for about 87.5 per cent in comparison to the exclusive use of a calcium hydroxide dressing. The application of mineral trioxide aggregate within the apical part of the root canal was unproblematical. Reducing the number of appointments, it is possible to reduce the stress factor of young patients and their parents. The use of digital radiography also contributes to reduce the fear of parents regarding high radiation dosis. Keywords: apical barrier formation, calcium hydroxide, mineral trioxide aggregate